Raster graphics operations/Ruby
The Code
Collecting all the Ruby code from Category:Raster graphics operations, so one can invoke: require 'raster_graphics'
Uses the ChunkyPNG pure-Ruby PNG library. Important to note won't work with `frozen_string_literal: true` uses mutable String operations.
###########################################################################
# frozen_string_literal: false
###########################################################################
# Represents an RGB[http://en.wikipedia.org/wiki/Rgb] colour.
class RGBColour
# Red, green and blue values must fall in the range 0..255.
def initialize(red, green, blue)
ok = [red, green, blue].inject(true) { |ok, c| ok &= c.between?(0, 255) }
raise ArgumentError, "invalid RGB parameters: #{[red, green, blue].inspect}" unless ok
@red = red
@green = green
@blue = blue
end
attr_reader :red, :green, :blue
alias r red
alias g green
alias b blue
# Return the list of [red, green, blue] values.
# RGBColour.new(100,150,200).values # => [100, 150, 200]
# call-seq:
# values -> array
#
def values
[@red, @green, @blue]
end
# Equality test: two RGBColour objects are equal if they have the same
# red, green and blue values.
# call-seq:
# ==(a_colour) -> true or false
#
def ==(a_colour)
values == a_colour.values
end
# Comparison test: compares two RGBColour objects based on their #luminosity value
# call-seq:
# <=>(a_colour) -> -1, 0, +1
#
def <=>(a_colour)
luminosity <=> a_colour.luminosity
end
# Calculate a integer luminosity value, in the range 0..255
# RGBColour.new(100,150,200).luminosity # => 142
# call-seq:
# luminosity -> int
#
def luminosity
Integer(0.2126 * @red + 0.7152 * @green + 0.0722 * @blue)
end
# Return a new RGBColour value where all the red, green, blue values are the
# #luminosity value.
# RGBColour.new(100,150,200).to_grayscale.values # => [142, 142, 142]
# call-seq:
# to_grayscale -> a_colour
#
def to_grayscale
l = luminosity
self.class.new(l, l, l)
end
# Return a new RGBColour object given an iteration value for the Pixmap.mandelbrot
# method.
def self.mandel_colour(i)
new(16 * (i % 15), 32 * (i % 7), 8 * (i % 31))
end
RED = RGBColour.new(255, 0, 0)
GREEN = RGBColour.new(0, 255, 0)
BLUE = RGBColour.new(0, 0, 255)
YELLOW = RGBColour.new(255, 255, 0)
BLACK = RGBColour.new(0, 0, 0)
WHITE = RGBColour.new(255, 255, 255)
end
###########################################################################
# A Pixel represents an (x,y) point in a Pixmap.
Pixel = Struct.new(:x, :y)
###########################################################################
class Pixmap
def initialize(width, height)
@width = width
@height = height
@data = fill(RGBColour::WHITE)
end
attr_reader :width, :height
def fill(colour)
@data = Array.new(@width) { Array.new(@height, colour) }
end
def validate_pixel(x, y)
unless x.between?(0, @width - 1) && y.between?(0, @height - 1)
raise ArgumentError, "requested pixel (#{x}, #{y}) is outside dimensions of this bitmap"
end
end
###############################################
def [](x, y)
validate_pixel(x, y)
@data[x][y]
end
alias get_pixel []
def []=(x, y, colour)
validate_pixel(x, y)
@data[x][y] = colour
end
alias set_pixel []=
def each_pixel
if block_given?
@height.times { |y| @width.times { |x| yield x, y } }
else
to_enum(:each_pixel)
end
end
###############################################
# write to file/stream
PIXMAP_FORMATS = %w[P3 P6].freeze # implemented output formats
PIXMAP_BINARY_FORMATS = ['P6'].freeze # implemented output formats which are binary
def write_ppm(ios, format = 'P6')
raise NotImplementedError, "pixmap format #{format} has not been implemented" unless PIXMAP_FORMATS.include?(format)
ios.puts format, "#{@width} #{@height}", '255'
ios.binmode if PIXMAP_BINARY_FORMATS.include?(format)
each_pixel do |x, y|
case format
when 'P3' then ios.print @data[x][y].values.join(' '), "\n"
when 'P6' then ios.print @data[x][y].values.pack('C3')
end
end
end
def save(filename, opts = { format: 'P6' })
File.open(filename, 'w') do |f|
write_ppm(f, opts[:format])
end
end
alias write save
def print(opts = { format: 'P6' })
write_ppm($stdout, opts[:format])
end
def save_as_jpeg(filename, quality = 75)
# using the ImageMagick convert tool
pipe = IO.popen("convert ppm:- -quality #{quality} jpg:#{filename}", 'w')
write_ppm(pipe)
rescue SystemCallError => e
warn "problem writing data to 'convert' utility -- does it exist in your $PATH?"
ensure
begin
pipe.close
rescue StandardError
false
end
end
def save_as_png(filename)
require 'chunky_png'
stream = StringIO.new('', 'r+')
each_pixel { |x, y| stream << self[x, y].values.pack('ccc') }
stream.seek(0)
ChunkyPNG::Canvas.extend(ChunkyPNG::Canvas::StreamImporting)
canvas = ChunkyPNG::Canvas.from_rgb_stream(width, height, stream)
canvas.to_image.save(filename)
end
###############################################
# read from file/pipe
def self.read_ppm(ios)
format = ios.gets.chomp
width, height = ios.gets.chomp.split.map(&:to_i)
max_colour = ios.gets.chomp
if !PIXMAP_FORMATS.include?(format) ||
(width < 1) || (height < 1) ||
(max_colour != '255')
ios.close
raise StandardError, "file '#{filename}' does not start with the expected header"
end
ios.binmode if PIXMAP_BINARY_FORMATS.include?(format)
bitmap = new(width, height)
bitmap.each_pixel do |x, y|
# read 3 bytes
red, green, blue = case format
when 'P3' then ios.gets.chomp.split
when 'P6' then ios.read(3).unpack('C3')
end
bitmap[x, y] = RGBColour.new(red, green, blue)
end
ios.close
bitmap
end
def self.open(filename)
read_ppm(File.open(filename, 'r'))
end
def self.open_from_jpeg(filename)
raise ArgumentError, "#{filename} does not exists or is not readable." unless File.readable?(filename)
begin
pipe = IO.popen("convert jpg:#{filename} ppm:-", 'r')
read_ppm(pipe)
rescue SystemCallError => e
warn "problem reading data from 'convert' utility -- does it exist in your $PATH?"
ensure
begin
pipe.close
rescue StandardError
false
end
end
end
###############################################
# conversion methods
def to_grayscale
gray = self.class.new(@width, @height)
each_pixel do |x, y|
gray[x, y] = self[x, y].to_grayscale
end
gray
end
def to_blackandwhite
hist = histogram
# find the median luminosity
median = nil
sum = 0
hist.keys.sort.each do |lum|
sum += hist[lum]
if sum > @height * @width / 2
median = lum
break
end
end
# create the black and white image
bw = self.class.new(@width, @height)
each_pixel do |x, y|
bw[x, y] = self[x, y].luminosity < median ? RGBColour::BLACK : RGBColour::WHITE
end
bw
end
def save_as_blackandwhite(filename)
to_blackandwhite.save(filename)
end
###############################################
def draw_line(p1, p2, colour)
validate_pixel(p1.x, p2.y)
validate_pixel(p2.x, p2.y)
x1 = p1.x
y1 = p1.y
x2 = p2.x
y2 = p2.y
steep = (y2 - y1).abs > (x2 - x1).abs
if steep
x1, y1 = y1, x1
x2, y2 = y2, x2
end
if x1 > x2
x1, x2 = x2, x1
y1, y2 = y2, y1
end
deltax = x2 - x1
deltay = (y2 - y1).abs
error = deltax / 2
ystep = y1 < y2 ? 1 : -1
y = y1
x1.upto(x2) do |x|
pixel = steep ? [y, x] : [x, y]
self[*pixel] = colour
error -= deltay
if error.negative?
y += ystep
error += deltax
end
end
end
###############################################
def draw_line_antialised(p1, p2, colour)
x1 = p1.x
y1 = p1.y
x2 = p2.x
y2 = p2.y
steep = (y2 - y1).abs > (x2 - x1).abs
if steep
x1, y1 = y1, x1
x2, y2 = y2, x2
end
if x1 > x2
x1, x2 = x2, x1
y1, y2 = y2, y1
end
deltax = x2 - x1
deltay = (y2 - y1).abs
gradient = 1.0 * deltay / deltax
# handle the first endpoint
xend = x1.round
yend = y1 + gradient * (xend - x1)
xgap = (x1 + 0.5).rfpart
xpxl1 = xend
ypxl1 = yend.truncate
put_colour(xpxl1, ypxl1, colour, steep, yend.rfpart * xgap)
put_colour(xpxl1, ypxl1 + 1, colour, steep, yend.fpart * xgap)
itery = yend + gradient
# handle the second endpoint
xend = x2.round
yend = y2 + gradient * (xend - x2)
xgap = (x2 + 0.5).rfpart
xpxl2 = xend
ypxl2 = yend.truncate
put_colour(xpxl2, ypxl2, colour, steep, yend.rfpart * xgap)
put_colour(xpxl2, ypxl2 + 1, colour, steep, yend.fpart * xgap)
# in between
(xpxl1 + 1).upto(xpxl2 - 1).each do |x|
put_colour(x, itery.truncate, colour, steep, itery.rfpart)
put_colour(x, itery.truncate + 1, colour, steep, itery.fpart)
itery += gradient
end
end
def put_colour(x, y, colour, steep, c)
x, y = y, x if steep
self[x, y] = anti_alias(colour, self[x, y], c)
end
def anti_alias(new, old, ratio)
blended = new.values.zip(old.values).map { |n, o| (n * ratio + o * (1.0 - ratio)).round }
RGBColour.new(*blended)
end
###############################################
def draw_circle(pixel, radius, colour)
validate_pixel(pixel.x, pixel.y)
self[pixel.x, pixel.y + radius] = colour
self[pixel.x, pixel.y - radius] = colour
self[pixel.x + radius, pixel.y] = colour
self[pixel.x - radius, pixel.y] = colour
f = 1 - radius
ddF_x = 1
ddF_y = -2 * radius
x = 0
y = radius
while x < y
if f >= 0
y -= 1
ddF_y += 2
f += ddF_y
end
x += 1
ddF_x += 2
f += ddF_x
self[pixel.x + x, pixel.y + y] = colour
self[pixel.x + x, pixel.y - y] = colour
self[pixel.x - x, pixel.y + y] = colour
self[pixel.x - x, pixel.y - y] = colour
self[pixel.x + y, pixel.y + x] = colour
self[pixel.x + y, pixel.y - x] = colour
self[pixel.x - y, pixel.y + x] = colour
self[pixel.x - y, pixel.y - x] = colour
end
end
###############################################
def flood_fill(pixel, new_colour)
current_colour = self[pixel.x, pixel.y]
queue = Queue.new
queue.enqueue(pixel)
until queue.empty?
p = queue.dequeue
next unless self[p.x, p.y] == current_colour
west = find_border(p, current_colour, :west)
east = find_border(p, current_colour, :east)
draw_line(west, east, new_colour)
q = west
while q.x <= east.x
%i[north south].each do |direction|
n = neighbour(q, direction)
queue.enqueue(n) if self[n.x, n.y] == current_colour
end
q = neighbour(q, :east)
end
end
end
def neighbour(pixel, direction)
case direction
when :north then Pixel[pixel.x, pixel.y - 1]
when :south then Pixel[pixel.x, pixel.y + 1]
when :east then Pixel[pixel.x + 1, pixel.y]
when :west then Pixel[pixel.x - 1, pixel.y]
end
end
def find_border(pixel, colour, direction)
nextp = neighbour(pixel, direction)
while self[nextp.x, nextp.y] == colour
pixel = nextp
nextp = neighbour(pixel, direction)
end
pixel
end
###############################################
def median_filter(radius = 3)
radius += 1 if radius.even?
filtered = self.class.new(@width, @height)
$stdout.puts "processing #{@height} rows"
pb = ProgressBar.new(@height) if $DEBUG
@height.times do |y|
@width.times do |x|
window = []
(x - radius).upto(x + radius).each do |win_x|
(y - radius).upto(y + radius).each do |win_y|
win_x = 0 if win_x.negative?
win_y = 0 if win_y.negative?
win_x = @width - 1 if win_x >= @width
win_y = @height - 1 if win_y >= @height
window << self[win_x, win_y]
end
end
# median
filtered[x, y] = window.sort[window.length / 2]
end
pb.update(y) if $DEBUG
end
pb.close if $DEBUG
filtered
end
###############################################
def magnify(factor)
bigger = self.class.new(@width * factor, @height * factor)
each_pixel do |x, y|
colour = self[x, y]
(x * factor..x * factor + factor - 1).each do |xx|
(y * factor..y * factor + factor - 1).each do |yy|
bigger[xx, yy] = colour
end
end
end
bigger
end
###############################################
def histogram
histogram = Hash.new(0)
each_pixel do |x, y|
histogram[self[x, y].luminosity] += 1
end
histogram
end
###############################################
def draw_bezier_curve(points, colour)
# ensure the points are increasing along the x-axis
points = points.sort_by { |p| [p.x, p.y] }
xmin = points[0].x
xmax = points[-1].x
increment = 2
prev = points[0]
((xmin + increment)..xmax).step(increment) do |x|
t = 1.0 * (x - xmin) / (xmax - xmin)
p = Pixel[x, bezier(t, points).round]
draw_line(prev, p, colour)
prev = p
end
end
# the generalized n-degree Bezier summation
def bezier(t, points)
n = points.length - 1
points.each_with_index.inject(0.0) do |sum, (point, i)|
sum += n.choose(i) * (1 - t)**(n - i) * t**i * point.y
end
end
###############################################
def self.mandelbrot(width, height)
mandel = Pixmap.new(width, height)
pb = ProgressBar.new(width) if $DEBUG
width.times do |x|
height.times do |y|
x_ish = Float(x - width * 11 / 15) / (width / 3)
y_ish = Float(y - height / 2) / (height * 3 / 10)
mandel[x, y] = RGBColour.mandel_colour(mandel_iters(x_ish, y_ish))
end
pb.update(x) if $DEBUG
end
pb.close if $DEBUG
mandel
end
def self.mandel_iters(cx, cy)
x = y = 0.0
count = 0
while (Math.hypot(x, y) < 2) && (count < 255)
x, y = (x**2 - y**2 + cx), (2 * x * y + cy)
count += 1
end
count
end
###############################################
# Apply a convolution kernel to a whole image
def convolute(kernel)
newimg = Pixmap.new(@width, @height)
pb = ProgressBar.new(@width) if $DEBUG
@width.times do |x|
@height.times do |y|
apply_kernel(x, y, kernel, newimg)
end
pb.update(x) if $DEBUG
end
pb.close if $DEBUG
newimg
end
# Applies a convolution kernel to produce a single pixel in the destination
def apply_kernel(x, y, kernel, newimg)
x0 = [0, x - 1].max
y0 = [0, y - 1].max
x1 = x
y1 = y
x2 = [@width - 1, x + 1].min
y2 = [@height - 1, y + 1].min
r = g = b = 0.0
[x0, x1, x2].zip(kernel).each do |xx, kcol|
[y0, y1, y2].zip(kcol).each do |yy, k|
r += k * self[xx, yy].r
g += k * self[xx, yy].g
b += k * self[xx, yy].b
end
end
newimg[x, y] = RGBColour.new(luma(r), luma(g), luma(b))
end
# Function for clamping values to those that we can use with colors
def luma(value)
if value.negative?
0
elsif value > 255
255
else
value
end
end
end
###########################################################################
# Utilities
class ProgressBar
def initialize(max)
$stdout.sync = true
@progress_max = max
@progress_pos = 0
@progress_view = 68
$stdout.print "[#{'-' * @progress_view}]\r["
end
def update(n)
new_pos = n * @progress_view / @progress_max
if new_pos > @progress_pos
@progress_pos = new_pos
$stdout.print '='
end
end
def close
$stdout.puts '=]'
end
end
class Queue # < Array
alias enqueue push
alias dequeue shift
end
class Numeric
def fpart
self - truncate
end
def rfpart
1.0 - fpart
end
end
class Integer
def choose(k)
factorial / (k.factorial * (self - k).factorial)
end
def factorial
(2..self).reduce(1, :*)
end
end
A Test Suite
def display_pixmap(filename)
puts "displaying #{filename}"
system "./ppmview.rb #{filename} &"
end
###########################################################################
if $0 == __FILE__
old_debug = $DEBUG
$DEBUG = true
# for testing
class Pixmap
def ==(a_bitmap)
return false if @width != a_bitmap.width or @height != a_bitmap.height
@width.times {|x| @height.times {|y|
return false if not self[x,y] == (a_bitmap[x,y])
}}
true
end
end
require 'test/unit'
class TestRGBColour < Test::Unit::TestCase
def test_init
color = RGBColour.new(0,100,200)
assert_equal(100, color.g)
end
def test_constants
assert_equal([255,0,0], [RGBColour::RED.r,RGBColour::RED.g,RGBColour::RED.b])
assert_equal([0,255,0], [RGBColour::GREEN.r,RGBColour::GREEN.g,RGBColour::GREEN.b])
assert_equal([0,0,255], [RGBColour::BLUE.r,RGBColour::BLUE.g,RGBColour::BLUE.b])
end
def test_error
color = RGBColour.new(0,100,200)
assert_raise(ArgumentError) {RGBColour.new(0,0,256)}
end
end
class TestPixmap < Test::Unit::TestCase
def setup
@w = 20
@h = 30
@bitmap = Pixmap.new(@w,@h)
end
def test_init
assert_equal(@w, @bitmap.width)
assert_equal(@h, @bitmap.height)
assert_equal(RGBColour::WHITE, @bitmap.get_pixel(10,10))
end
def test_fill
@bitmap.fill(RGBColour::RED)
assert_equal(255,@bitmap[10,10].red)
assert_equal(0,@bitmap[10,10].green)
assert_equal(0,@bitmap[10,10].blue)
end
def test_get_pixel
assert_equal(@bitmap[5,6], @bitmap.get_pixel(5,6))
assert_raise(ArgumentError) {@bitmap[100,100]}
end
def test_grayscale
@bitmap.fill(RGBColour::BLUE)
@bitmap.height.times {|y| [9,10,11].each {|x| @bitmap[x,y]=RGBColour::GREEN}}
@bitmap.width.times {|x| [14,15,16].each {|y| @bitmap[x,y]=RGBColour::GREEN}}
@bitmap.save('testcross.ppm')
Pixmap.open('testcross.ppm').to_grayscale.save('testgray.ppm')
end
def test_save
@bitmap.fill(RGBColour::BLUE)
filename = 'test.ppm'
@bitmap.save(filename)
expected_size = 3 + (@w.to_s.length + 1 + @h.to_s.length + 1) + 4 + (@w * @h * 3)
assert_equal(expected_size, File.size(filename))
end
def test_open
@bitmap.fill(RGBColour::RED)
@bitmap.set_pixel(10,15, RGBColour::WHITE)
filename = 'test.ppm'
@bitmap.save(filename)
new = Pixmap.open(filename)
assert(@bitmap == new)
end
end
# a green cross on a blue background
colour_bitmap = Pixmap.new(20, 30)
colour_bitmap.fill(RGBColour::BLUE)
colour_bitmap.height.times {|y| [9,10,11].each {|x| colour_bitmap[x,y]=RGBColour::GREEN}}
colour_bitmap.width.times {|x| [14,15,16].each {|y| colour_bitmap[x,y]=RGBColour::GREEN}}
colour_bitmap.save('testcross.ppm')
display_pixmap 'testcross.ppm'
Pixmap.open('testcross.ppm').to_grayscale.save('testgray.ppm')
image = Pixmap.open('testcross.ppm')
image.save_as_jpeg('testcross.jpg')
#image.print(:format => "P3")
bitmap = Pixmap.open_from_jpeg('testcross.jpg')
savefile = 'testcross_from_jpeg.ppm'
bitmap.save(savefile)
display_pixmap savefile
bitmap = Pixmap.new(500, 500)
bitmap.fill(RGBColour::BLUE)
10.step(430, 60) do |a|
bitmap.draw_line(Pixel[10, 10], Pixel[490,a], RGBColour::YELLOW)
bitmap.draw_line(Pixel[10, 10], Pixel[a,490], RGBColour::YELLOW)
end
bitmap.draw_line(Pixel[10, 10], Pixel[490,490], RGBColour::YELLOW)
savefile = 'testlines4.ppm'
bitmap.save(savefile)
display_pixmap savefile
bitmap = Pixmap.new(30, 30)
bitmap.draw_circle(Pixel[14,14], 12, RGBColour::BLACK)
savefile = 'testcircle.ppm'
bitmap.save(savefile)
display_pixmap savefile
bitmap = Pixmap.new(300, 300)
bitmap.draw_circle(Pixel[149,149], 120, RGBColour::BLACK)
bitmap.draw_circle(Pixel[200,100], 40, RGBColour::BLACK)
bitmap.flood_fill(Pixel[140,160], RGBColour::BLUE)
savefile = 'testflood.ppm'
bitmap.save(savefile)
display_pixmap savefile
bitmap = Pixmap.new(500, 500)
bitmap.fill(RGBColour::BLUE)
10.step(430, 60) do |a|
bitmap.draw_line_antialised(Pixel[10, 10], Pixel[490,a], RGBColour::YELLOW)
bitmap.draw_line_antialised(Pixel[10, 10], Pixel[a,490], RGBColour::YELLOW)
end
bitmap.draw_line_antialised(Pixel[10, 10], Pixel[490,490], RGBColour::YELLOW)
bitmap.save('testantialias.ppm')
display_pixmap 'testantialias.ppm'
file = 'teapot.ppm'
display_pixmap file
bitmap = Pixmap.open(file)
# test new grayscale
savefile = 'teapotgray.ppm'
gray = bitmap.to_grayscale
gray.save(savefile)
display_pixmap savefile
#
savefile = 'testfiltered.ppm'
filtered = bitmap.median_filter
filtered.save(savefile)
display_pixmap savefile
file = 'teapot.ppm'
savefile = 'teapotbw.ppm'
display_pixmap file
Pixmap.open(file).save_as_blackandwhite(savefile)
display_pixmap savefile
bitmap = Pixmap.new(400, 400)
points = [
Pixel[40,100], Pixel[100,350], Pixel[150,50],
Pixel[150,150], Pixel[350,250], Pixel[250,250]
]
points.each {|p| bitmap.draw_circle(p, 3, RGBColour::RED)}
bitmap.draw_bezier_curve(points, RGBColour::BLUE)
savefile = 'testbezier.ppm'
bitmap.save(savefile)
display_pixmap savefile
savefile = 'testmandel.ppm'
Pixmap.mandelbrot(500,500).save(savefile)
display_pixmap savefile
# Demonstration code using the teapot image from Tk's widget demo
teapot = Pixmap.open('teapot.ppm')
[ ['Emboss', [[-2.0, -1.0, 0.0], [-1.0, 1.0, 1.0], [0.0, 1.0, 2.0]]],
['Sharpen', [[-1.0, -1.0, -1.0], [-1.0, 9.0, -1.0], [-1.0, -1.0, -1.0]]],
['Blur', [[0.1111,0.1111,0.1111],[0.1111,0.1111,0.1111],[0.1111,0.1111,0.1111]]],
].each do |label, kernel|
savefile = 'test' + label.downcase + '.ppm'
teapot.convolute(kernel).save(savefile)
display_pixmap savefile
end
$DEBUG = old_debug
end
An Image Viewer
The ppmview.rb program is:
#!/usr/bin/ruby
require 'tk'
if ARGV.empty?
$stderr.puts "usage: #{File.basename($0)} imagefile"
exit 1
end
filename = ARGV.shift
unless File.readable?(filename)
raise ArgumentError, "can't read file '#{filename}'"
end
root = TkRoot.new('title' => File.basename(filename))
label = TkLabel.new(root) {image TkPhotoImage.new('file' => filename)}
label.pack
Tk.mainloop